Numerous manufacturing processes require a means to support a workpiece, without causing damage, so that an operation can be effected thereon, particularly an operation which applies a force or pressure to the workpiece, such as a printed circuit board (PCB) during printing or population. The face of the workpiece to be supported may not necessarily be planer, as demonstrated by the example of a two-sided electronics assembly; at least one application requires tooling to support a three dimensional face.
There are several known apparatuses, which utilize elongated support members, which conform to the profile of the contact surface of the workpiece.
Thyberg et al. teach an apparatus using a multiplicity of hard balls and the application of pressure to the balls to provide a simple and effective locking mechanism. The elongated support members include ridges formed perpendicular to the axis of motion, whereby pressure (shown as by displacing the balls with an additional member) can be applied to the multiplicity of hard balls to effectively lock about the said ridges.
Frosch et al. teach a plurality of spindles (elongated support members), which contour to the workpiece and are secured in position using a locking piston associated with each spindle (or pair of spindles). The elongated support members are raised to the workpiece using springs.
Barozzi teaches a multiplicity of parallel pins in parallel rows, which utilize friction to arrest the pins to the respective position. The frictional locking means consist of elastic elements interpositioned with elastic deformation between each of the parallel rows of pins. Barozzi utilizes flat springs located along parallel pins.
Dougherty et al. teach an anvil (plurality of elongated support members) having a uniquely configurable face where the elongated support members are raised by a fluid (air, fluid, or similar) directly contacting the pins. The pins are then retained against any downward force by individual sleeves with slits that are placed about the shaft of the pins; the sleeves are compressed inwardly when under external pressure exerted by elastomeric tubes that enclosed the slit sleeves.
Puettmer, et al. teach a profiled clamping jaw, whereby the profiling process utilizes a fluid and individual needle valves to raise and hold the plurality of pins to a contour. The apparatus comprises of a complex system to individually move and hold each clamping ram (elongated support member) in position. The system does not allow the removal of any of the clamping rams.
Beale teaches an apparatus that provides support for a predetermined position raising and lowering only specified support members. Beale further teaches an apparatus which can secure a workpiece to a fixture using thin clamping foils which will not damage or interfere with the screen printing process.
Each of the above contouring support apparatuses is limited where they do not provide a means for easy removal or re-installation of any of the elongated support members.
The two parent applications disclose several apparatuses for supporting a workpiece using a plurality of elongated support members, which adjust to conform to the profile of the surface of the workpiece to be supported.
The flexible, self-conforming workpiece support systems disclosed in the parent applications, as well as similar apparatuses such as the cited arts may be subjected to harsh environments such as solder printing. Solder paste, used during the solder printing process, is known to drop into the solder printing apparatus. The solder paste comprises of small (approximately 0.0008″ diameter) spheres of solder (tin lead) mixed in flux paste to a viscosity of approximately 1×10^6 centipoise. When dried, the solder paste may have properties similar to clay or cement. The small particles of solder may act as abrasives.
The flexible, self-conforming workpiece support systems disclosed in the parent applications, as well as similar apparatuses such as the cited arts may provide an upward force to the workpiece during the profiling process. This said upward force could cause the workpiece to flex upwards.
What is desired is a system, which is flexible, can automatically create a profile to support the face of any workpiece, including a non-planer surface, and minimizes any forces transferred to the said face. The system should be designed to be repeatable, serviceable, and with minimal complexity. Further, the system should incorporate a method, features and or accessories to increase repeatability and reliability.